Electro-optical device

ABSTRACT

A liquid crystal electro-optical device comprising a pair of substrates at least one of them is light-transmitting, electrodes being provided on said substrates, and an electro-optical modulating layer being supported by said pair of substrates, provided that said electro-optical modulating layer comprises an anti-ferroelectric liquid crystal material or a smectic liquid crystal material which exhibits anti-ferroelectricity, and a transparent material.

This is a Divisional application of Ser. No. 08/447,549, filed May 23,1995, now U.S. Pat. No. 5,566,009; which is a continuation of Ser. No.08/024,946, filed Mar. 2, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Industrial Field of Application

The present invention relates to a polymer dispersed liquid crystalelectro-optical device comprising a liquid crystal/resin compositecomposed of a high molecular resin having dispersed therein a liquidcrystal material. More particularly, it relates to a liquid crystalelectro-optical device having a high scattering efficiency.

2. Prior Art

Conventional liquid crystal electro-optical devices include the wellknown and practically used devices operating in a TN (twisted nematic)or an STN (super twisted nematic) mode. These liquid crystalelectro-optical devices are based on nematic liquid crystal and thelike. Furthermore, devices using ferroelectric liquid crystals haverecently come to our knowledge. Those known liquid crystalelectro-optical devices basically comprise a first and a secondsubstrate each having established thereon an electrode and a lead, and aliquid crystal composition being incorporated therebetween. By takingthis assembly, the state of the liquid crystal molecules can be variedby applying an electric field to the liquid crystal composition, becausethe liquid crystal material itself has an anisotropy in dielectricconstant, or, in the case of a ferroelectric liquid crystal, it exhibitsspontaneous polarization. The electro-optical effect which resultstherefrom is made use of in the aforementioned liquid crystalelectro-optical devices.

In a liquid crystal electro-optical device operating in a TN or STNmode, an alignment treatment, i.e., rubbing, is applied to align theliquid crystal molecules along the rubbing direction at each of theplanes in contact with the two substrates by which the liquid crystallayer is sandwiched. Rubbing is applied to the upper and the lowerplanes as such that their directions may be displaced by 90° or by anangle between 200° and 290° from each other. Accordingly, theintermediate liquid crystal molecules in the liquid crystal layer, i.e.,those between the upper and the lower molecules positioned at an angleof from 90° to 290° adjacent to the substrates arrange themselves into aspiral to achieve a configuration of lowest energy. In the case of anSTN type liquid crystal device, a chiral substance is optionally addedto the liquid crystal material if necessary.

The aforementioned devices, however, require polarizer sheets to beincorporated. Moreover, the liquid crystal molecules need to beregularly arranged in the liquid crystal electro-optical device toachieve a predetermined alignment. The alignment treatment as referredherein comprises rubbing an alignment film (ordinarily an organic film)with a cotton or a velvet cloth along one direction. If not for thistreatment, the liquid crystal molecules are unable to attain apredetermined alignment, and hence, no electro-optical effect can beexpected therefrom. Accordingly, conventional liquid crystalelectro-optical devices above unexceptionably comprise a pair ofsubstrates which make a container to hold therein a liquid crystalmaterial. Then, the optical effect which results from the orientedliquid crystal having charged into the container can be utilized.

There is also known another type of liquid crystal, a polymer dispersedliquid crystal (referred to sometimes hereinafter as PDLC), which can beused without incorporating any polarizer sheets and applying analignment treatment and the like. In FIG. 7 is shown schematically aPDLC. A PDLC electro-optical device comprises a solid polymer 4 havingdispersed therein a granular or sponge-like liquid crystal material 3between a pair of light-transmitting substrates 1 to give alight-control layer. A liquid crystal device of this type can befabricated by dispersing microcapsules of a liquid crystal material in apolymer, and then forming a thin film thereof on a substrate or a film.The liquid crystal material can be encapsulated using, for example, gumarabic, poly(vinyl alcohol), and gelatin.

In the case of liquid crystal molecules being encapsulated in poly(vinylalcohol), for example, if they show a positive dielectric anisotropy inthe thin film, an electric field may be applied in such a manner thattheir major axes may be arranged in parallel with the electric field.Accordingly, a transparent state can be realized if the refractive indexof the encapsulated liquid crystal is equal to that of the polymer. Whenno electric field is applied, the liquid crystal microcapsules take arandom orientation and the incident light is scattered because therefractive index of the liquid crystal greatly differs from that of thepolymer. Thus, an opaque or a milky white state is realized. In FIG. 8is shown the change of transmittance in relation with the appliedvoltage in the liquid crystal electro-optical device above. Thetransmittance changes with increasing and decreasing voltage asindicated with arrows in the figure. If the liquid crystal microcapsuleshave a negative dielectric anisotropy and if the average refractiveindex of the liquid crystal is equal to that of poly(vinyl alcohol), atransparent state can be realized by applying no electric field.

The term “average refractive index” as referred herein is defined asfollows. When no electric field is applied to a liquid crystal materialon a non-treated substrate, the refractive indices thereof are found tobe distributed as shown in FIG. 10. In the figure, no and ne representthe refractive index for an ordinary light and an extraordinary light,respectively. The “average refractive index” is then defined as theindex n_(ave) at the maximum distribution intensity in the curve asshown in FIG. 10.

In the presence of an electric field, on the other hand, a milky whiteor an opaque state results, because the liquid crystal molecules arearranged as such that the major axes thereof make a right angle withrespect to the direction of the electric field to thereby develop adifference in refractive index. A similar result is obtained if theliquid crystal molecules themselves exhibit spontaneous polarizationalong a direction vertical to the major axes of the liquid crystalmolecules. In such a case, the transmittance changes with increasing ordecreasing voltage as shown in FIG. 9. In this manner, a PDLCelectro-optical device provides various types of information by makingthe best of the difference between the transparent and the opaque state.

Polymer dispersed liquid crystals include not only those of theencapsulated type, but also those comprising liquid crystal materialsbeing dispersed in an epoxy resin, or those utilizing phase separationbetween a liquid crystal and a resin which results by irradiating alight for curing a photocurable resin being mixed with a liquid crystal,or those obtained by impregnating a three-dimension polymer network witha liquid crystal. All those enumerated above are referred to as “polymerdispersed liquid crystals” in the present invention.

Because the electro-optical devices using PDLCs are free of polarizersheets, they yield a far higher light transmittance as compared with anyof the conventional electro-optical devices operating on TN mode, STNmode, etc. More specifically, because the light transmittance perpolarizer sheet is as low as about 50%, the light transmittance of anactive matrix display using a combination of polarizer sheets as aresult falls to a mere 1%. In an STN type device, the transmittanceresults as low as 20%. Accordingly, an additional backlighting isrequisite to compensate for the optical loss to lighten those darkdisplays. In the case of a PDLC electro-optical device, by contrast, 50%or more of light is transmitted. This is clearly an advantage of adevice using no polarizer sheets.

Because a PDLC takes two states, i.e., a transparent state and an opaquestate, and transmits more light when used in a liquid crystalelectro-optical device, the R & D efforts are more paid for developingdevices of a light transmitting type. More specifically, particularnotice is taken to a light-transmitting liquid crystal electro-opticaldevice of a projection type.

A projection type liquid crystal electro-optical device comprisesplacing the liquid crystal electro-optical device panel on a light pathof a light beam being generated from a light source, and then projectingthe light against a flat panel through a slit being provided at apredetermined angle. If the liquid crystal molecules in the liquidcrystal panel have a positive dielectric anisotropy, they take a randomorientation to realize an opaque (milky white) state in the low electricfield region; i.e., at any voltage below a threshold voltage at whichthe liquid crystal molecules do not respond to the applied voltage. Thelight incident to a panel at such a state is scattered to widen thelight path. The light having scattered then proceeds to the slit, butmost of them are cut off to yield a dark state on the flat panel.

On the other hand, when the liquid crystal molecules respond to theapplied electric field and when they are thereby arranged in parallelwith the direction of the electric field, a light incident theretopasses straight forward to yield a bright state at a high contrast onthe flat panel. When the liquid crystal molecules have a negativedielectric anisotropy, or when they have spontaneous polarization alonga direction vertical to the major axes of the molecules, and if theaverage refractive index of the liquid crystal molecules coincide withthat of the polymer resin matrix, the liquid crystal electro-opticaldevice panel turns transparent when no electric field is applied; itreversely turns opaque to yield a dark state by scattering the lightwhen an electric field is applied.

As described in the foregoing, the switching of states of a PDLC occurs,in principle, by the scattering of light. That is, in passing throughthe light control layer comprising the resin and the liquid crystaldroplets which differ from each other in terms of refractive index, thelight incident on the transparent substrate side greatly changes itscourse each time it comes to the boundary between the resin and theliquid crystal. Accordingly, the incident light reaches the substrate onthe other side in a completely scattered state. To increase thescattering efficiency of the light control layer, it is preferred thatthe liquid crystal droplets are more frequently brought into contactwith the resin along the thickness direction of the light control layer.The more the boundary between a resin and a liquid crystal droplet isprovided for a light, the more scattered the light becomes. Accordingly,the scattering efficiency can be increased by providing a thickercontrol layer. However, a thicker control layer adversely increases thespacing between the substrates, that is, the distance between theelectrodes. A longer distance between the electrodes require a largerdriving voltage for switching the light control layer. This makes itimpossible to drive the liquid crystal cell with an ordinary IC(integrated circuit), particularly with a TFT (thin film transistor).

A practically feasible liquid crystal electro-optical device should, ingeneral,

1) be driven at a low voltage;

2) have rapid response; and

3) be driven at a speed of 0.1 msec (100 lsec) or less even in a cellhaving a thickness in the range of from 2.5 to 10 μm.

Most of the conventional PDLC electro-optical devices are based on anematic liquid crystal material, and are yet to satisfy the requiredquick response. No liquid crystal electro-optical device which satisfyall of the requirements enumerated above and still capable of providinga rapid optical response to dynamic displays without using any polarizersheets is proposed to present. However, a PDLC electro-optical deviceusing a ferroelectric liquid crystal material is known as a device whichsatisfy a part of the requirements above. This type of liquid crystalelectro-optical device, however, because of the ferroelectric nature ofthe liquid crystal, exhibits a piezoelectric effect while it is driven.More specifically, the liquid crystal being incorporated between theelectrodes undergoes shrinking by the electric field being applied fordriving the liquid crystal, and such a change in volume initiatesvibration of the substrates as a source of noise. Furthermore, such avibration of the substrates my cause damage to the liquid crystalelectro-optical device due to the peeling off which occurs on the pairof substrates which are adhered to make a cell.

SUMMARY OF THE INVENTION

The present invention has been accomplished with an aim to provide aliquid crystal electro-optical device free of the aforementionedproblems. Accordingly, the present invention provides an electro-opticaldevice comprising a pair of substrates at least one of which istransparent; an electro-optical modulating layer provided between saidsubstrates and comprising an antiferroelectric liquid crystal and atransparent material; and means for applying an electric field to saidantiferroelectric liquid crystal. Said means comprises an active matrixcircuit. The liquid crystal electro-optical device according to thepresent invention is therefore improved in response speed and freed fromthe problems attributed to change in volume of the liquid crystalmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron micrograph showing the cross section of the lightcontrol layer of a liquid crystal electro-optical device according to anembodiment of the present invention;

FIG. 2 is a schematically drawn cross sectional view of liquid crystalelectro-optical devices according to embodiments of the presentinvention;

FIG. 3 is a schematically drawn cross sectional view of a liquid crystalelectro-optical device according to an embodiment of the presentinvention, in a step of the fabrication process;

FIG. 4 shows a circuit diagram for active matrix addressing;

FIG. 5 shows another circuit diagram for active matrix addressing and avoltage-tilt angle characteristic curve for an anti-ferroelectric liquidcrystal;

FIG. 6 shows a structure for active matrix addressing;

FIG. 7 is a schematically drawn cross sectional view of a polymerdispersed liquid crystal electro-optical device;

FIG. 8 is a graph showing the change of transmittance with increasingand decreasing voltage of a polymer dispersed liquid crystalelectro-optical device in which a liquid crystal material having apositive dielectric anisotropy is used;

FIG. 9 is a graph showing the change of transmittance with increasingand decreasing voltage of a polymer dispersed liquid crystalelectro-optical device in which a liquid crystal material having anegative dielectric anisotropy or a liquid crystal material exhibitingspontaneous polarization along a direction vertical to the major axis ofthe liquid crystal molecule is used;

FIG. 10 shows schematically a distribution of refractive indices withina liquid crystal;

FIG. 11 shows schematically the liquid crystal molecule alignment of apolymer dispersed liquid crystal electro-optical device when no electricfield is applied; and

FIG. 12 shows schematically the liquid crystal molecule alignment of apolymer dispersed liquid crystal electro-optical device wen an electricfield is applied.

Fig. 13 illustrates driver circuits and an active matrix circuit formedon a substrate.

DETAILED DESCRIPTION OF THE INVENTION

The liquid crystal droplets to be dispersed in the light control layeraccording to the present invention can be prepared by any of the threerepresentative fabrication processes as follows.

(1) A 4:6 to 8:2 mixture of a liquid crystal material and an ultraviolet(UV) curable resin is injected between a pair of substrates, and a UVlight is irradiated thereto from the surface of the substrate to curethe resin. Preferably, on irradiating UV light to the mixture, thesample is previously heated to a temperature about 5 to 40° C. higherthan the transition temperature at which the mixture of the liquidcrystal and the resin undergoes transition from an isotropic phase to aliquid crystal phase.

(2) A solution having previously prepared by dissolving a liquid crystaland a resin in a solvent is applied to the surface of a substrate by aspinner process or by casting, and the solvent is gradually evaporated.The resin for use in this process include polyethylene terephthalate),polyfumarates, polycarbazoles, and PMMA [poly(methyl methacrylate)].

(3) A liquid crystal is encapsulated with poly(vinyl alcohol) to obtainmicrocapsules of the liquid crystal.

As shown in FIG. 2(A), spherical liquid crystal drop lets 104 can beobtained by any of the processes above. In FIG. 7, those sphericaldroplets 3 can also be seen. In FIG. 2(A) and FIG. 7 are shown basicliquid crystal cells using a liquid crystal material according to thepresent invention. Needless to say, liquid crystal displays having aknown active matrix structure can be fabricated making use of thepresent invention as well. In FIGS. 2(B) and 2(C) a re shown activematrices using a reverse stagger type TFT and a coplanar TFT,respectively.

The present invention is illustrated in greater detail referring tonon-limiting examples below. It should be understood, however, that thepresent invention is not to, be construed as being limited thereto.

EXAMPLE 1

As shown in FIG. 2(A), a polymer dispersed liquid crystal was fabricatedfirst by a known process. The present Example refers to a polymerdispersed liquid crystal using a UV curable resin. A transparentconductive coating, i.e., an ITO (Indium-Tin-Oxide) film 102, wasdeposited on a light-transmitting substrate 101 by a known vapordeposition or sputtering process to a thickness of from 500 to 2,000Å.The ITO film thus obtained had a sheet resistivity of from 20 to 200Ω/cm . The film thus obtained was patterned by an ordinaryphotolithographic process. The resulting first and second substrateswere adhered together under pressure, while maintaining a spacing offrom 5 to 100 μm, preferably from 7 to 30 μm, by incorporating aninorganic spacer between the substrates. In this manner, the cellspacing can be maintained constant at about the diameter of the spacer.As the liquid crystal material, an ester based anti-ferroelectric liquidcrystal having a refractive index of 1.6 and a an of 0.2 was mixed witha photocurable resin having a refractive index of 1.573 and comprising amixed system of an urethane oligomer and an acrylic monomer.

The aforementioned mixed material was stirred and subjected toultrasonic vibration to obtain a homogeneous mixture. The mixing waseffected by heating the mixture while applying stirring and ultrasonicvibration to obtain a homogeneous mixture as a liquid of an isotropicphase, and the resulting mixture was cooled to obtain a liquid crystalphase. This method was found very effective for obtaining the desiredliquid crystal mixed system.

The resulting liquid crystal mixed system was injected between the firstand the second substrates above at a temperature higher than the S_(A)-Iphase transition temperature of the liquid crystal mixed system, and anUV light was irradiated thereto at an intensity of from about 10 to 100mW/cm² for a duration of from about 30 to 300 seconds to cure the resinwhile allowing the mixed system to undergo phase separation into aliquid crystal and a resin. As a result, liquid crystal droplets 104surrounded by a resin (transparent material) 105 were formed.

The liquid crystal device thus obtained scatters light when no electricfield is applied between the electrodes having established on the upperand the lower substrates, because the liquid crystal molecules arearranged in a random orientation. When a voltage is applied to theelectrodes, on the other hand, the liquid crystal molecules align alonga particular direction according to the direction of the electric field.At this state, light can be transmitted by the electro-optical effectwhich is generated by the anisotropy in refractive index of the liquidcrystal material. A maximum light transmission can be achieved if therefractive index of the liquid crystal material along the direction oflight transmittance is equal to that of the light-transmitting substanceon applying an electric field.

The liquid crystal material used in the present Example undergoes aphase transition sequence of Iso-SmA-SmC_(A)*-Cry. More specifically, itundergoes phase transition from Iso to SmA at 92° C., from SmA toSmC_(A)* at 60° C., and from SmC_(A)* to Cry at −20° C. It has apositive dielectric anisotropy with a birefringence Δn of about 0.2, anda spontaneous polarization of 12 nC/cm²

The liquid crystal electro-optical device thus obtained yielded aswitching rate at 25° C. of 40 μsec, and the corresponding responsespeed was high. It required a relative high threshold voltage of from 5to 9 V/μm for driving the liquid crystal. However, because the liquidcrystal electro-optical device of the present invention has a high lightscattering efficiency, the device itself can be made thinner by reducingthe spacing between the substrates and hence the driving voltage can bereduced to a level well comparable to a generally employed voltage.

Because an anti-ferroelectric liquid crystal material is used in thedevice according to the present invention, the shrinkage of the liquidcrystal material due to volume change thereof on applying an electricfield for driving the device can be considerably reduced as comparedwith that of a ferroelectric liquid crystal material. Thus, no vibrationoccurs on the substrate of the liquid crystal electro-optical deviceaccording to the present invention.

Furthermore, a higher contrast can be achieved with a liquid crystalelectro-optical device comprising an antiferroelectric smectic liquidcrystal according to the present invention. This is ascribed to the factthat the smectic layer structure, i.e., the structure which theanti-ferroelectric liquid crystal material takes in the disperseddroplets, can be deformed by the electric field being applied thereto.Thus, the refractive index of the liquid crystal material can be greatlydiffered from that of the transparent material comprising a resin. Thisis in clear contrast with the case using a ferroelectric liquid crystalmaterial, because the smectic layer structure of the ferroelectricliquid crystal material as dispersed droplets cannot be deformed by anexternal electric field.

EXAMPLE 2

An active matrix addressed liquid crystal cell using the liquid crystalmaterial described in Example 1 was fabricated. Referring to FIG. 2(B),the fabrication process is described below. An ITO coating 112 wasdeposited on a first substrate 111 by a known sputtering process to athickness of from 5 to 200 nm. A soda-lime glass substrate was used asthe first substrate 111. If a TFT is to be formed directly on the firstsubstrate, the use of an alkali-free glass substrate is preferred fromthe viewpoint of preventing the TFT from being contaminated by analkali.

A black coating was formed in stripes to give black stripes 121 to avoidexposure of amorphous silicon of the TFT to external light. Thus was thefirst substrate completed.

An amorphous silicon TFT 117 having a gate insulator 118 based onsilicon nitride was established by a known process on a second substratemade of an alkali—free glass such as a Corning 7059. A polyimide film119 which serves as an interlayer insulator and also as a smoothinglayer was formed at a thickness of from 200 to 1000 nm. Then, dataconnections 120 for an active matrix were formed using Cr, and a pixelelectrode 113 using ITO was established further thereon to complete thesecond substrate.

The first and the second substrates thus obtained were adhered togetherin the same manner as in Example 1 by incorporating spacers (not shownin the Figure) to maintain a distance between the substrates in a rangeof from 5 to 100 μm, preferably, from 7 to 30 μm. Then, the same liquidcrystal material as that used in Example 1 was injected into theresulting cell structure, and UV light at an intensity of from about 10to 100 mW/cm² was irradiated to the liquid crystal material from thefirst substrate side to cure the resin. Thus was obtained liquid crystaldroplets 114 being surrounded by the resin 115. At this point, theliquid crystal material portion under the black stripes 121 remainsuncured, because this portion is not necessary for the display.

The active matrix addressed liquid crystal panel thus obtained comprisesa circuit structure as shown in FIG. 4(A). In FIG. 4(A) is given a part,i.e., a 2×2 matrix of the entire structure. The planar view of thesecond substrate of the present Example is given in FIG. 6(A). Referringto FIG. 6(A), a pixel electrode 404 and a TFT 403 are provided in aregion defined by a gate line (scan line) 401 and a data line 402. Then,connections for pixel matrix were provided to the liquid crystal panelby a known TAB (tape automated bonding) process, and a voltage at aproper level was applied to each of the connections to confirm thedisplay of images.

EXAMPLE 3

An active matrix addressed liquid crystal cell using the liquid crystalmaterial described in Example 1 was fabricated. Referring to FIG. 2(C),the fabrication process is described below. An ITO coating 132 wasdeposited on a first substrate 131 by a known sputtering process to athickness of from 5 to 200 nm. A soda-lime glass substrate was used asthe first substrate 131. If a TFT is to be formed directly on the firstsubstrate, the use of an alkali-free glass substrate is preferred fromthe viewpoint of preventing the TFT from being contaminated by analkali. Black stripes 141 were also formed in the same manner as inExample 2. Thus was the first substrate completed.

A polycrystalline silicon (polysilicon) TFT 137 having a gate insulator138 based on silicon oxide was established by a known process on asecond substrate made of a heat-resistant alkali-free glass such as aCorning 1733 and quartz glass. An interlayer insulator 139 was formed onthe TFT element 137 at a thickness of from 200 to 1000 nm. Then, dataconnections 140 for the active matrix were formed using Cr, and a pixelelectrode 133 using ITO was established further thereon to complete thesecond substrate.

The first and the second substrates thus obtained were adhered togetherin the same manner as in Example 1 by incorporating therebetween spacers(not shown in the Figure) to maintain a distance between the substratesin a range of from 5 to 100 μm, preferably, from 7 to 30 μm. Then, thesame liquid crystal material as that used in Example 1 was injected intothe resulting cell structure, and UV light at an intensity of from about10 to 100 mW/cm² was irradiated to the liquid crystal material from thefirst substrate side to cure the resin. Thus was obtained liquid crystaldroplets 134 being surrounded by the resin 135. At this point, theliquid crystal material portion under the black stripes 141 remainsuncured, because this portion is not necessary for the display.

The active matrix addressed liquid crystal panel thus obtained comprisesa circuit structure as shown in FIG. 4(A). In FIG. 4(A) is given a part,i.e., a 2×2 matrix of the entire structure. A driver circuit was formedtogether on the same substrate of the liquid crystal panel of thepresent Example. FIG. 13 illustrates a configuration of driver circuits62 and an active Matrix circuit 63 formed on a substrate 61 inaccordance with the present Example. Accordingly, no external drivercircuit was necessary for the present liquid crystal panel. Thus,required signals were externally input to the liquid crystal panel toconfirm the display of images.

EXAMPLE 4

An active matrix addressed liquid crystal cell of a CMOS (complementaryMOS) transfer gate type using the liquid crystal material described inExample 1 was fabricated. The circuit structure of the matrix fabricatedin the present Example is shown in FIG. 4(B). An N-channel TFT (NTFT)and a P-channel TFT (PTFT) were established on a single pixel, so thatthey may function in a complementary manner. Thus, the active matrixcircuit for applying an electric field to the antiferroelectric liquidcrystal may comprise at least two transistors having differentconductivity types from each other for each pixel of the electro-opticaldevice in accordance with the present invention. Black stripes and anITO transparent conductive film were formed on the first substrate inthe same manner as in Examples 2 and 3.

The process for fabricating the second substrate is described belowmaking special reference to the fabrication of a CMOS TFT (CTFT). Thefabrication steps are shown schematically by a cross section view inFIG. 3. The second substrate may be made from a heat resistantalkali-free glass such as Corning 1733 glass and quartz glass, but inthis Example, an N/O glass (a product of Nippon Electric Glass Co.,Ltd.) was used. The N/O glass has an excellent heat resistance and athermal expansion coefficient equal to that of quartz, but containselements unfavorable for a TFT, such as Li, at a considerable amount.Thus, a silicon nitride coating 202 was formed on the second substrateat a thickness of from 20 to 200 nm to prevent the unfavorable alkalielements from influencing the overlying TFT. Furthermore, a 100 to 1,000nm thick silicon oxide coating 203 was deposited thereon by sputteringto provide a basecoating for the TFT.

Then, a substantially intrinsic semiconductor film, which may be eitheramorphous or polycrystalline, an amorphous silicon film 204, forexample, was formed at a thickness of from 50 to 500 nm on thebasecoating obtained above. This was followed by the deposition of asilicon oxide film 205 at a thickness of from 10 to 100 nm bysputtering, for use as a cap. The resulting structure was then annealedat 600° C. for 60 hours in a nitrogen atmosphere to effectrecrystallization. Thus was obtained a structure as shown in FIG. 3(A).

The resulting structure was then patterned into islands to establish anNTFT region 207 and a PTFT region 206.

Then, a silicon oxide film was deposited as a gate insulator 208 at athickness of from 50 to 150 nm thereon by ECR (electron cyclotronresonance) plasma-assisted CVD (chemical vapor deposition) process or bysputtering, and a 500 nm thick aluminum coating was deposited furtherthereon by sputtering. The aluminum coating was patterned to establishgate electrode portions 209 and 210 for the PTFT and NTFT, respectively.The channel was provided at a length of 8 μm and a width of 8 μm. Theresulting structure is illustrated in FIG. 3(B).

Then, electric current was applied to the gate electrode portions, i.e.,gate electrodes with connections 209 and 210, to form aluminum oxidecoatings 211 and 212 on and to the surroundings (upper and sidesurfaces) of the portions 209 and 210 by an anodic oxidation process.The anodic oxidation process was conducted under the same conditions asthose described in the inventions provided by the present inventors, asare disclosed in Japanese patent application Nos. 4-30220 and 4-38637.Thus was obtained an anodically oxidized film at a thickness of about350 nm.

Phosphorus as an N-type impurity was then introduced into theisland-like semiconductor portions 206 and 207 by ion implantation,using the gate electrode portions 211 and 212 as the masks according toa self-aligned process. Further then, the NTFT portion only was coveredwith, for example, a photoresist as a masking material 219 as shown inFIG. 3(C), and boron as a P-type impurity was introduced into theportion 206 in a self-aligned manner. In this manner were obtained theP-type impurity regions 213 and 215, as well as the N-type impurityregions 216 and 218. Channel regions 214 and 217 for PTFT and NTFT,respectively, were also obtained as a consequence.

After conducting ion doping, the amorphous regions having resulted byimpurity injection were activated by subjecting them to laser annealingas illustrated in FIG. 3(D). The conditions for the laser annealing arethe same as those described in the previous inventions of the presentauthors, as disclosed in Japanese patent application Nos. 4-30220 and4-38637. Furthermore, after establishing interlayer insulators 220 and221, contact holes were bore, and a chromium coating was providedthereon by sputtering. The chromium coating thus obtained was patternedto establish connections 222, 223, and 224 to obtain a structure asshown in FIG. 3(E).

Finally, a polyimide coating 225 was provided on the second substrate bya known spin-coating process to smooth the surface. Then, a contact holewas formed thereon to establish a pixel electrode 226 using ITO tocomplete the second substrate.

The first and the second substrates thus obtained were adhered togetherin the same manner as in Example 1 by incorporating therebetween spacersto maintain a distance between the substrates in a range of from 5 to100 μm, preferably, from 7 to 30 Ξm. Then, the same liquid crystalmaterial as that used in Example 1 was injected into the resulting cellstructure, and UV light at an intensity of from about 10 to 100 mW/cm²was irradiated to the liquid crystal material from the first substrateside to cure the resin. Thus was obtained liquid crystal droplets beingsurrounded by the resin.

The active matrix addressed liquid crystal panel thus obtained comprisesa circuit structure as shown in FIG. 4(B). In FIG. 4(B) is given a part,i.e., a 2×2 matrix of the entire structure. A driver circuit was formedtogether on the same substrate of the liquid crystal panel of thepresent Example as in the liquid crystal panel obtained in Example 3.Accordingly, no external driver circuit was necessary for the presentliquid crystal panel. Thus, for driving the circuit of the presentExample, a method as described in the previous invention of the presentinventors, as disclosed in Japanese patent application No. 3-208648, maybe employed. The liquid crystal panel thus obtained in the presentExample was driven according to substantially the same method disclosedin the aforementioned Japanese patent application No. 3-208648 toconfirm the display of images.

EXAMPLE 5

An active matrix addressed liquid crystal cell of a CMOS transfer gatetype using the liquid crystal material described in Example 1 wasfabricated. The circuit structure of the matrix fabricated in thepresent Example is shown in FIG. 4(C). An N channel TFT (NTFT) and a Pchannel TFT (PTFT) were established on a single pixel, so that they mayfunction in a complementary manner. In FIG. 6(B) is shown a plan viewfor the circuit established on the second substrate of the presentExample. The circuit comprises a region defined by a first and a secondscan line 411 and 412, respectively, and a data line 413, in which apixel electrode 416, an NTFT 414, and a PTFT 415 are established.

The first and the second substrates were fabricated essentially in thesame process as described in Example 4, except for the circuitarrangement. The first and the second substrates thus obtained wereadhered together in the same manner as in Example 1. The same liquidcrystal material as that used in Example 1 was injected into theresulting cell structure, and UV light at an intensity of from about 10to 100 mW/cm² was irradiated to the liquid crystal material from thefirst substrate side. to cure the resin. Thus was obtained liquidcrystal droplets being surrounded by the resin.

For driving the circuit of the present Example, a method as disclosed inJapanese patent application Nos. 63-82177 and 63-966361 may be employed.The liquid crystal panel thus obtained in the present Example was drivenaccording to substantially the same method disclosed in theaforementioned Japanese patent application No. 63-82177 to confirm thedisplay of images.

EXAMPLE 6

An active matrix addressed liquid crystal cell of a CMOS inverter typeusing the liquid crystal material described in Example 1 was fabricated.The circuit structure of the matrix fabricated in the present Example isshown in FIG. 4(D). As shown in the figure, it was designed as such thatan N-channel TFT (NTFT) and a P-channel TFT (PTFT) may be established ona single pixel, so that they may function in a complementary manner. InFIG. 6(C) is shown a plan view for the circuit established on the secondsubstrate of the present Example. The circuit comprises a region definedby a first and a second scan line 421 and 422, respectively, and a dataline 423, in which a pixel electrode 426, an NTFT 424, and a PTFT 425are established.

The first and the second substrates were fabricated essentially in thesame process as described in Example 4, except for the circuitarrangement. The first and the second substrates thus obtained wereadhered together in the same manner as in Example 1. The same liquidcrystal material as that used in Example 1 was injected into theresulting cell structure, and UV light at an intensity of from about 10to 100 mW/cm² was irradiated to the liquid crystal material from thefirst substrate side to cure the resin. Thus was obtained liquid crystaldroplets being surrounded by the resin.

For driving the circuit of the present Example, a method as described inthe previous invention of the present inventors, as disclosed inJapanese patent application No. 3-163871, may be employed. The liquidcrystal panel thus obtained in the present Example was driven accordingto substantially the same method disclosed in the aforementionedJapanese patent application No. 3-163871 to confirm the display ofimages.

EXAMPLE 7

An active matrix addressed liquid crystal cell of an advanced CMOSinverter type using the liquid crystal material described in Example 1was fabricated. The circuit structure of the matrix fabricated in thepresent Example is shown in FIG. 4(E). As shown in the figure, itcomprises a CMOS inverter in a single pixel and a switching transistorbeing provided on the scan line connected thereto. That is, the circuitaccording to the present Example is different from that of Example 6 inthat it economizes on scan lines; i.e., the aperture ratio can beincreased because one scan line is sufficient for the entire singlepixel array.

The first and the second substrates were fabricated essentially in thesame process as described in Example 4, except for the circuitarrangement. The first and the second substrates thus obtained wereadhered together in the same manner as in Example 1. The same liquidcrystal material as that used in Example 1 was injected into theresulting cell structure, and UV light at an intensity of from about 10to 100 mW/cm² was irradiated to the liquid crystal material from thefirst substrate side to cure the resin. Thus was obtained liquid crystaldroplets being surrounded by the resin.

For driving the circuit of the present Example, a method as described inthe previous invention of the present inventors, as disclosed inJapanese patent application No. 3-169308, may be employed. The liquidcrystal panel thus obtained in the present Example was driven accordingto substantially the same method disclosed in the aforementionedJapanese patent application No. 3-169308 to confirm the display ofimages.

EXAMPLE 8

An active matrix addressed liquid crystal cell of an advanced CMOSbuffer type using the liquid crystal material described in Example 1 wasfabricated. The circuit structure of the matrix fabricated in thepresent Example is shown in FIG. 4(F). As shown in the figure, itcomprises a CMOS buffer in a single pixel, and a switching transistorbeing provided on the scan line connected thereto. That is, the circuitaccording to the present Example economizes on scan lines; i.e., theaperture ratio can be increased because one scan line is sufficient forthe entire single pixel array.

The first and the second substrates were fabricated essentially in thesame process as described in Example 4, except for the circuitarrangement. The first and the second substrates thus obtained wereadhered together in the same manner as in Example 1. The same liquidcrystal material as that used in Example 1 was injected into theresulting cell structure, and UV light at an intensity of from about 10to 100 mW/cm² was irradiated to the liquid crystal material from thefirst substrate side to cure the resin. Thus was obtained liquid crystaldroplets being surrounded by the resin.

For driving the circuit of the present Example, a method as described inthe previous invention of the present inventors, as disclosed inJapanese patent application No. 3-169307, may be employed. The liquidcrystal panel thus obtained in the present Example was driven accordingto substantially the same method disclosed in the aforementionedJapanese patent application No. 3-169307 to confirm the display ofimages.

EXAMPLE 9

As shown in FIG. 7, a polymer dispersed liquid crystal was fabricatedfirst by a known process. The present Example refers to a polymerdispersed liquid crystal using a UV curable resin. A transparentconductive coating, i.e., an ITO film 2, was deposited on alight-transmitting substrate 1 by a known vapor deposition or sputteringprocess to a thickness of from 500 to 2,000 Å. The ITO film thusobtained had a sheet resistivity of from 20 to 200 Ω/cm². The film thusobtained was patterned by an ordinary photolithographic process. Theresulting first and second substrates were adhered together underpressure, while maintaining a spacing of from 5 to 100 μm, preferablyfrom 7 to 30 μm, by incorporating an inorganic spacer between thesubstrates. In this manner, the cell spacing can be maintained constantat about the diameter of the spacer. As the liquid crystal material, anester based anti-ferroelectric liquid crystal having a refractive indexof 1.6 and a Δn of 0.2 was mixed with a photocurable resin having arefractive index of 1.62 and comprising a mixed system of an urethaneoligomer and an acrylic monomer.

The aforementioned mixed material was stirred and subjected toultrasonic vibration to obtain a homogeneous mixture. The mixing waseffected by heating the mixture while applying stirring and ultrasonicvibration to obtain a homogeneous mixture as a liquid of an isotropicphase, and the resulting mixture was cooled to obtain a liquid crystalphase. This method was found very effective for obtaining the desiredliquid crystal mixed system.

The resulting liquid crystal mixed system was injected between the firstand the second substrates above at a temperature higher than the S_(A)-Iphase transition temperature of the liquid crystal mixed system, and anUV light was irradiated thereto at an intensity of from about 10 to 100mW/cm² for a duration of from about 30 to 300 seconds to cure the resinwhile allowing the mixed system to undergo phase separation into aliquid crystal and a resin. As a result, liquid crystal droplets 3surrounded by a resin 4 were formed.

The electro-optical modulating layer of the liquid crystal device asshown in FIG. 11 thus obtained transmits a light incident thereon whenno electric voltage (no electric signal) is applied to theelectro-optical modulating layer between the electrodes havingestablished on the upper and the lower substrates, because the liquidcrystal molecules 1 are arranged in a random orientation and the averagerefractive index of the liquid crystal is almost equal to that of theresin in the random orientation. When a voltage (an electric signal) isapplied to the electro-optical modulating layer, on the other hand, theliquid crystal molecules align themselves in such a manner that themajor axes thereof be vertical to the direction of the applied electricfield owing to the spontaneous polarization 2 of the liquid crystalmolecules 1. At this state, a difference in refractive index isgenerated between the liquid crystal and the polymer resin and theelectro-optical modulating layer scatters a light incident thereon.

The liquid crystal material used in the present Example undergoes aphase transition sequence of Iso-SmA-SmC*-SmC_(A)*-Cry. Morespecifically, it undergoes phase transition from Iso to Sm_(A) at 100°C., from SmA to SmC* at 84° C., from SmC* to SmC_(A) at 82° C., and fromSmC_(A)* to Cry at −10.1° C. It has a dielectric anisotropy with abirefringence In of about 0.2, and a spontaneous polarization of 80nC/cm². The electro-optical characteristics of the liquid crystalelectro-optical device comprising the antiferroelectric liquid crystalthus obtained are listed in Table 1.

TABLE 1 Transmittance Threshold Voltage Response Speed 95%(0 V) 9.5V/μm(when increasing a voltage)  8.0 μsec. (0->80 V) 56%(80 V) 5.5V/μm(when decreasing a voltage) 306 μsec. (80->0 V)

The values given in Table 1 are the characteristics at 80° C. As can beclearly read from the transmittance, a PDLC using an anti-ferroelectricliquid crystal material yields a voltage-transmittance relation as shownin FIG. 9. This is in clear contrast to that shown in FIG. 8, whichcorresponds to a voltage-transmittance curve of a conventional PDLC. Theliquid crystal electro-optical device thus obtained yielded a far higherswitching rate as compared to that of a device using a conventionalnematic liquid crystal material, hence yielding a higher response speed.It required a relative high threshold voltage for driving the liquidcrystal as shown in Table 1. However, because the liquid crystal may bereplaced by another one having a higher birefringence, i.e., a liquidcrystal having a higher light scattering power, the device itself can bemade thinner by reducing the spacing between the substrates.Accordingly, the driving voltage can be reduced to a level wellcomparable to a generally employed voltage.

Because an anti-ferroelectric liquid crystal material is used in thedevice according to the present invention, the shrinkage of the liquidcrystal material due to volume change thereof on applying an electricfield for driving the device can be considerably reduced as comparedwith that of a ferroelectric liquid crystal material. Thus, no vibrationoccurs on the substrate of the liquid crystal electro-optical deviceaccording to the present invention.

Furthermore, a higher contrast can be achieved with a liquid crystalelectro-optical device according to the present invention. This isascribed to the fact that the smectic layer structure, i.e., thestructure which the anti-ferroelectric liquid crystal material takes inthe dispersed droplets, can be deformed by the electric field beingapplied thereto. Thus, the refractive index of the liquid crystalmaterial can be greatly differed from that of the transparent substance.This is in clear contrast with the case using a ferroelectric liquidcrystal material, because the smectic layer structure of theferroelectric liquid crystal material as dispersed droplets cannot bedeformed by an external electric field.

It should be further added that the liquid crystal material used in thepresent invention shows a hysteresis in the threshold voltagecharacteristics because it is based on an antiferroelectric liquidcrystal material. This is advantageous in realizing an electro-opticaldevice having far improved in response time and a memory function, ascompared with the conventional PDLC devices based on a nematic or aferroelectric liquid crystal.

In the present specification, the dispersed liquid crystal materialswere described as droplets, and they were expressed with circles orspherical shapes in the drawings. However, the liquid crystal materialsare not restricted to droplets or those having circular shapes, and thesame effect as on those above may also be expected on the liquid crystalmaterials present in other shapes and forms. For example, as shown inthe micrograph of FIG. 1, a three-dimensional network, which is theresin observed as a white portion, may be present between the substratesand the liquid crystal may be held in the cavities provided therein.

Furthermore, a dichroic dye and the like may be added to theelectro-optical modulating layer to fabricate a liquid crystalelectro-optical device of a guest-host type.

In addition, the matrix circuits used in Examples 2, 3, 4, 5, and 6 maybe replaced by those shown in FIGS. 5(A), 5(B), 5(C), and 5(D).

In FIG. 5(E) is shown the tilt angle of the antiferroelectric liquidcrystal molecules on applying a voltage to the anti-ferroelectric liquidcrystal material according to the present invention. It can be seen thatthe anti-ferroelectric liquid crystal molecules can be stabilized at alarger tilt angle by applying thereto a voltage being stabilized at avalue higher than the threshold voltage. However, a fluctuation in theapplied voltage may destabilize the anti-ferroelectric liquid crystalmolecules. In the circuits illustrated in FIGS. 5(A), 5(B), 5(C), and5(D), capacitors are provided to absorb such fluctuations and to therebystabilize the anti-ferroelectric liquid crystal molecules to assure astable display on a liquid crystal electro-optical device.

As described in detail in the foregoing, the present invention providesa PDLC electro-optical device having a high scattering efficiency underno applied electric field and favorable light transmittingcharacteristics under an applied electric field. The present inventionalso provides another type of a PDLC electro-optical device havingfavorable light transmitting characteristics under no applied electricfield and a high scattering efficiency under an applied electric field.

In the former type of the liquid crystal electro-optical device, aswitching speed of 40 μsec or even higher is obtained; i.e., a devicehaving a quick response of 100 or more times as quick as that of aconventional device is obtained even on a cell having an inter electrodespacing (thickness of the electro-optical modulating layer) of from 5 to10 μm. Furthermore, the use of an anti-ferroelectric liquid crystal asthe liquid crystal material results in a favorable dielectric propertywith a relative dielectric constant of 10 to 100. This enablesrealization of a higher switching rate even on a device having a lowelectric field intensity, i.e., on such having a thick liquid crystalcell or such under a low voltage. This is because, if the electric fieldwere to be maintained constant, a higher relative dielectric constantsignifies that a higher force can be exerted to the liquid crystalmolecules for their aligning.

In the latter type of the liquid crystal electro-optical device, aswitching speed of 400 μsec or even higher is obtained; i.e, a devicehaving a quick response of 20 or more times as quick as that of aconventional device is obtained even on a cell having an inter electrodespacing of from 5 to 10 μm. Furthermore, the use of ananti-ferroelectric liquid crystal as the liquid crystal material resultsin a favorable dielectric property with a spontaneous polarization aslarge as 80 nC/cm². This enables realization of a higher switching rateeven on a device to which only an electric field of low intensity can beapplied, i.e., on such having a thick liquid crystal cell or such undera low voltage. This is because, if the electric field were to bemaintained constant, a higher spontaneous polarization signifies that ahigher force can be exerted to the liquid crystal molecules for theirdriving.

The conventional ferroelectric liquid crystal devices comprisingpolarizer sheets comprised cells as thin as from 1.3 to 2.3 μm inthickness. However, they were not practically feasible because they weretoo thin and were therefore apt to cause short circuit between the upperand the lower substrate electrodes due to contaminations and the like.This problem could be overcome by increasing the interelectrode spacingto a length of from 2.5 to 10 μm. An electro-optical device having acell thickness of 5 μm, for example, was substantially free of shortcircuit, and a switching time of 500 μsec or shorter could be obtainedthereon at a little expense of reduced electric field intensity. Inparticular, a switching time of 100 μsec or even shorter was obtained onan electro-optical device of the former type referred hereinbefore.

It should be noted, moreover, that conventional PDLC electro-opticaldevices based on nematic liquid crystals had no hysteresis in thethreshold voltage characteristics and hence no memory function of thedisplay. In the liquid crystal electro-optical device according to thepresent invention, the use of an anti-ferroelectric liquid crystalmaterial yields a threshold voltage of 9.5 V/μm on applying an electricfield to effect the transition from a light-transmitting state to ascattering state. On cutting off the electric field to effect thetransition from a light-scattering state to a light-transmitting state,the threshold voltage is, however, 5.5 V/μm. This clear hysteresis canbe taken the best for use as a memory.

Furthermore, a bright liquid crystal display which suffers less opticalloss was realized by using no polarizer sheets. That is, a liquidcrystal panel having a paper-like appearance with a milky whitebackground was obtained. In particular, an image of high contrast can berealized by combining the liquid crystal material of the presentinvention with an active matrix. Accordingly, a display having anappearance similar to that of a printed matter was realized.

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A liquid crystal device comprising: a firstsubstrate and a second substrate; a black stripe formed over said firstsubstrate; at least one thin film transistor formed over said secondsubstrate, said thin film transistor comprising a gate electrode, a gateinsulating film formed on the gate electrode, a semiconductor layer oversaid gate electrode with said gate insulating film interposedtherebetween; a smoothing layer comprising an organic resin formed oversaid second substrate and said thin film transistor; a pixel electrodeformed over the smoothing layer and connected to said thin filmtransistor through a first opening of the smoothing layer; a data lineformed over the smoothing layer and connected to said thin filmtransistor through a second opening of the smoothing layer wherein saidpixel electrode and said data line are formed on a same layer: and anoptical modulating layer comprising a liquid crystal material interposedbetween said first and second substrates, wherein said black stripecovers [at least] said semiconductor layer.
 2. The liquid crystal deviceof claim 1 wherein said pixel electrode is transparent and comprisesindium tin oxide.
 3. The liquid crystal device of claim 1 wherein saidsmoothing layer comprises polyimide.
 4. The liquid crystal device ofclaim 1 wherein a thickness of said smoothing layer is 200 to 1000 nm.5. The liquid crystal device of claim 1 wherein said liquid crystalmaterial comprises an antiferroelectric liquid crystal.
 6. The liquidcrystal device of claim 5 wherein said liquid crystal material isdispersed into a resin.
 7. The liquid crystal device of claim 1 furthercomprising a film comprising indium tin oxide between said firstsubstrate and said black stripe.
 8. The liquid crystal device of claim 1wherein said semiconductor layer comprises amorphous silicon.
 9. Aliquid crystal device comprising: a first substrate and a secondsubstrate; a black stripe formed over said first substrate; at least onethin film transistor formed over said second substrate, said thin filmtransistor comprising a gate electrode, a gate insulating film formed onthe gate electrode, a semiconductor layer over said gate electrode withsaid gate insulating film interposed therebetween; a smoothing layercomprising an organic resin formed over said second substrate and saidthin film transistor; a pixel electrode formed over the smoothing layerand connected to said thin film transistor through a first opening ofthe smoothing layer; a data line formed over said smoothing layer andelectrically connected to said thin film transistor through a secondopening of the smoothing layer wherein said pixel electrode and saidthin film transistor are formed on a same layer; and an opticalmodulating layer comprising a liquid crystal material interposed betweensaid first and second substrates, wherein said black stripe covers saidsemiconductor layer and a portion where said pixel electrode isconnected to said thin film transistor.
 10. The liquid crystal device ofclaim 9 wherein said pixel electrode is transparent and comprises indiumtin oxide.
 11. The liquid crystal device of claim 9 wherein saidsmoothing layer comprises polyimide.
 12. The liquid crystal device ofclaim 9 wherein a thickness of said smoothing layer is 200 to 1000 nm.13. The liquid crystal device of claim 9 wherein said liquid crystalmaterial comprises an antiferroelectric liquid crystal.
 14. The liquidcrystal device of claim 13 wherein said liquid crystal material isdispersed into a resin.
 15. The liquid crystal device of claim 9 furthercomprising a film comprising indium tin oxide between said firstsubstrate and said black stripe.
 16. The liquid crystal device of claim9 wherein said semiconductor layer comprises amorphous silicon.
 17. Aliquid crystal device comprising: a first substrate and a secondsubstrate; a black stripe formed over said first substrate; a switchingelement comprising at least one thin film transistor formed over saidsecond substrate, said thin film transistor comprising a gate electrode,a gate insulating film formed on the gate electrode, a semiconductorlayer over said gate electrode with said gate insulating film interposedtherebetween; a smoothing layer comprising an organic resin formed oversaid second substrate and said thin film transistor; a data line formedon said smoothing layer and connected to said semiconductor layer ofsaid thin film transistor through a hole of said smoothing layer; apixel electrode formed on the smoothing layer and operationallyconnected to said switching element through another hole of thesmoothing layer; and an optical modulating layer comprising a liquidcrystal material interposed between said first and second substrates,wherein said black stripe covers said semiconductor layer and a portionwhere said data line is connected to said thin film transistor.
 18. Theliquid crystal device of claim 17 wherein said pixel electrode istransparent and comprises indium tin oxide.
 19. The liquid crystaldevice of claim 17 wherein said smoothing layer comprises polyimide. 20.The liquid crystal device of claim 17 wherein a thickness of saidsmoothing layer is 200 to 1000 nm.
 21. The liquid crystal device ofclaim 17 wherein said liquid crystal material comprises anantiferroelectric liquid crystal.
 22. The liquid crystal device of claim21 wherein said liquid crystal material is dispersed into a resin. 23.The liquid crystal device of claim 17 further comprising a filmcomprising indium tin oxide between said first substrate and said blackstripe.
 24. The liquid crystal device of claim 17 wherein saidsemiconductor layer comprises amorphous silicon.
 25. A liquid crystaldevice comprising; a first substrate and a second substrate; a blackstripe formed over said first substrate; a switching element comprisingat least one thin film transistor formed over said second substrate,said thin film- transistor comprising a gate electrode, a gateinsulating film formed on the gate electrode, a semiconductor layer oversaid gate electrode with said gate insulating film interposedtherebetween; a smoothing layer comprising an organic resin formed oversaid second substrate and said thin film transistor; a data line formedon the smoothing layer and connected to the semiconductor layer of saidthin film transistor through a hole of the smoothing layer; a pixelelectrode formed on the smoothing layer and electrically connected tosaid switching element through another hole of the smoothing layer; andan optical modulating layer comprising a liquid crystal materialinterposed between said first and second substrates, wherein said blackstripe covers said semiconductor layer and a portion where said pixelelectrode is connected to said thin film transistor.
 26. The liquidcrystal device of claim 25 wherein said pixel electrode is transparentand comprises indium tin oxide.
 27. The liquid crystal device of claim25 wherein said liquid crystal material comprises an antiferroelectricliquid crystal.
 28. The liquid crystal device of claim 25 wherein saidliquid crystal material is dispersed into a resin.
 29. The liquidcrystal device of claim 25 further comprising a film comprising indiumtin oxide between said first substrate and said black stripe.
 30. Theliquid crystal device of claim 25 wherein said semiconductor layercomprises amorphous silicon.
 31. A liquid crystal device comprising: afirst substrate and a second substrate; a black coating formed over saidfirst substrate; at least one thin film transistor formed over saidsecond substrate, said thin film transistor comprising a gate electrode,a gate insulating film formed on the gate electrode, a semiconductorlayer over said gate electrode with said gate insulating film interposedtherebetween; a smoothing layer comprising an organic resin formed oversaid second substrate and said thin film transistor; a pixel electrodeformed on the smoothing layer and connected to said thin film transistorthrough a first opening; [and] a data line formed on the smoothing layerand electrically connected to said thin film transistor; and an opticalmodulating layer comprising a liquid crystal material interposed betweensaid first and second substrates, wherein said black coating covers saidsemiconductor layer.
 32. The liquid crystal device of claim 31 whereinsaid pixel electrode is transparent and comprises indium tin oxide. 33.The liquid crystal device of claim 31 wherein said smoothing layercomprises polyimide.
 34. The liquid crystal device of claim 31 wherein athickness of said smoothing layer is 200 to 1000 nm.
 35. The liquidcrystal device of claim 31 further comprising a film comprising indiumtin oxide between said first substrate and said black coating.
 36. Theliquid crystal device of claim 31 wherein said semiconductor layercomprises amorphous silicon.
 37. The liquid crystal device of claim 31wherein said liquid crystal material is dispersed in a resin.
 38. Aliquid crystal device comprising: a first substrate and a secondsubstrate; a black coating formed over said first substrate; at leastone thin film transistor formed over said second substrate, said thinfilm transistor comprising a gate electrode, a gate insulating filmformed on the gate electrode, a semiconductor layer over said gateelectrode with said gate insulating film interposed therebetween; asmoothing layer comprising an organic resin formed over said secondsubstrate and said thin film transistor; a pixel electrode formed on thesmoothing layer and connected to said semiconductor layer through afirst opening of the smoothing layer; a data line formed on thesmoothing layer and electrically connected to said thin film transistorthrough a second opening of the smoothing layer: and an opticalmodulating layer comprising a liquid crystal material interposed betweensaid first and second substrates, wherein said black coating covers saidsemiconductor layer and a portion of said semiconductor layer at whichsaid pixel electrode is connected.
 39. The liquid crystal device ofclaim 38 wherein said pixel electrode is transparent and comprisesindium tin oxide.
 40. The liquid crystal device of claim 38 wherein saidsmoothing layer comprises polyimide.
 41. The liquid crystal device ofclaim 38 wherein a thickness of said smoothing layer is 200 to 1000 nm.42. A liquid crystal device comprising: a first substrate and a secondsubstrate; a black coating formed over said first substrate; a switchingelement comprising at least one thin film transistor formed over saidsecond substrate, said thin film transistor comprising a gate electrode,a gate insulating film adjacent to the gate electrode, a semiconductorlayer adjacent to said gate electrode with said gate insulating filminterposed therebetween; a smoothing layer comprising an organic resinformed over said second substrate and said thin film transistor; a pixelelectrode formed on the smoothing layer and electrically connected tosaid switching element through a first opening of the smoothing layer; adata line formed on the smoothing layer and electrically connected tosaid switching element through a second opening of the smoothing layer,and an optical modulating layer comprising a liquid crystal materialinterposed between said first and second substrates, wherein said blackcoating covers said semiconductor layer.
 43. A liquid crystal deviceaccording to claim 42 wherein said semiconductor layer comprisescrystalline silicon.
 44. A liquid crystal device according to claim 42wherein said semiconductor layer comprises amorphous silicon.
 45. Aliquid crystal device according to claim 42 wherein said gate electrodeis disposed below said semiconductor layer.